1. Field of the Invention
The present invention relates to a disk drive device to which power can be supplied from an interface and an external power source, and relates, for example, to a disk drive device suitable for a device with a USB (Universal Serial Bus) interface.
2. Description of Related Art
CD-R (Recordable) drives and CD-RW (Rewritable) drives of the CD family, which are disk drive devices capable of recording, have been widely introduced as removable storage devices for a personal computers.
In these disk drive devices, attempts have been made to increase the rotation speed of a disk. For recording, CD-Rs are currently capable of high speed recording at 16 or more times the standard speed, and CD-RWs are capable of high speed recording at 8 or 10 times the standard speed.
The USB (Universal Serial Bus) standard is a known interface standard for connecting peripherals to a personal computer. USB interfaces are provided with a power supply line, and many of the stand-alone type disk drive devices adopt such USB interfaces.
The current USB standard is USB 2.0, but USB 1.1, the previous standard, remains supported.
The USB 2.0 standard allows data transfer at 480 Mbps, while the USB 1.1 standard allows data transfer at a rate of up to 12 Mbps. Accordingly, with USB 1.1, data transfer is limited to a speed up to approximately 6 times the rated rotation speed of a disk. With USB 2.0, on the other hand, the disk rotation speed is not practically restricted by the data transfer rate.
In order to increase the data transfer rate of disk drive devices, not only the disk rotation speed, but also the processing speed of a data processor, a response of a servo circuit, and an access speed must be increased. Consequently, when the data transfer rate is increased, power consumption in substantially all circuits, including a disk servo circuit, a data processing circuit, a laser drive circuit, and a head servo circuit of an optical head, also increases.
Accordingly, there is a problem that under current conditions, even for a disk drive device compatible with USB 2.0, sufficient power cannot be supplied to the drive device through the USB interface, and thus attempts to increase the speed of the disk drive device are restricted by the power supply ability of the USB interface.
Therefore, in order to achieve high speed operation of the disk drive device, external power supply through an AC adaptor or the like is required. In other words, high speed disk drive devices can only be achieved when power is supplied from an external power source.
However, it is also necessary to consider the possibility that use of an external power source may not be appropriate in situations where power supply from the external power source is not possible or where use of a cable for connection to the external power source is undesirable, such as when the cable would be unsightly or on obstruction.